To further elaborate on my changing to mobil1 at 83k miles: I have had no burning/loss of oil with changing. The engine also seemed to run a bit better when I changed but that could be because I went from 10w-30 to 5w-30. I also go on much longer intervals than 3k miles. The oil stays noticeably cleaner and has been scientifically proven to break down less. I also feel with as hot as the zetec runs, running synthetic helps to prolong its life. Same thing goes for the cd4e, so I run mobil1 atf in it. Of course if the engine isn't in good condition, results are not gonna be the same, even on a nearly new engine, if the piston rings didn't get broken-in correctly, then leaks/oil usage could occur.